Visbreaking, deasphalting and hydrogenation of crude oils



May 5, 1964 H. BEUTHER ETAL VISBRAKING, DEASPHALTING AND HYDROGENATION OF' CRUDE OILS 2 Sheets-Sheet 1 Filed July 27, 1960 l terials are of low value.

- gravity below about 20 API.

United States Patent O VISBREAKING, DEASPHALTING AND HYDRGENATIN F CRUDE OILS Y Haroldeuther, Gibsonia, Richard A. Flinn, Pittsburgh,

and @laf A. Larson, ahmont, Pa., assiguors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Filed duly Z7, 1960, Ser. No. 45,709

Y 1 Claim. (Cl. 208--67) `materials and which have an API gravity below about 20 or topped or reduced crude-s containing asphaltic ma- Conversion of these heavy asphaltic lmaterials into hydrocarbons of higher value has been accomplished but such procedures 'are usually expensive or in many cases have undesirable aspects. For instance, it is known to hydrogenate such asphaltic materials to form catalytic cracking stocks. However, thorough conversion of asphaltic components, sulfur and metal .are used, the `subsequent catalytic cracking is not economical because of rapid deposit-ion of coke on the cracking catalyst from the unconve-rted asphal-tic materials. Also, metalliferous components are unconverted and poison the cracking catalyst. If the product from this moderate pressure process is` distilled to obtain a distillate catalytic cracking stock, the yield of this stock is low. It'is also known to deasphalt such heavy stocks and then subject them to a mild hydrogenation such as at about 1,000 p.s.i.V However the yields of useful products from such procedures have also been relatively low.

This invention has for its object to provide improved procedure for preparing valuable hydrocarbon products from heavy asphaltic containing crudes or tract-ions thereof. Another object is :to provide improved procedure for combined deasphalting and hydrogen treatment of asphalt containing crudes or topped or reduced crudes which have an APJ `gravity below about 20. Another object is to provide improved procedure for preparing a catalytic cracking stock and furnace oils in high yields `from asphalt containing crudes, toppedor reduced crudes having a A still yfurther object is to improve the state of the art. Other objects will appear hereinafter.

. These and other objects are accomplished by our invention which includes subjecting a crude or a topped 'or reduced crude having an API gravity below about 20 and containing asphaltic materials, i.e., a residual stock, to ya visbreaking operation, deasphalting the visbroken asphalt containing material,and subjectingthe visbroken and deasphalted material to treatment with hydrogen at a pressure between about 500 and 3,500 p.s.i. in the presence of va hydrogenation catalyst.

We have found in accordance with our inventionV that by treatment in this manner the deasphalting step is simplified `and a considerable increase in yield of valuable products, especially furnace oil, is obtained. Also, a product is obtained in high yield which constitutes a high quality catalytic cracking charge stock.

The residual feed stock used in our process may be any asphalt containing crude petroleum or any residual traction thereof -which has `an API gravity of below about 20. There are many petroleum crudes which are very viscous and high in asphaltic content and we contemplate the treatmentof such crudes without removal of any'of their components when they have a gravity below about 20.` On the other hand, most crudes are of higher gravity and with such crudes :it is desirable to remove valuable portions thereof in conventional manner and to obtain a residual fraction. This residual fraction may be prepared-by atmospheric or vacuum distillation.

The bisbreaking operation may be any such operation kno-Wn in the prior art. Although any degree of visbreaking may be employed it is advantageous to use conditions which form between about 4 and 20 percent gasoline. These Visbreaking operations are commonly carried out by passing the charge stock through a heating coil and heating the oil to a mild cracking temperature. The timeV of heating, the pressure and the temperature of heating control the .amount of thermal cracking or `conversion into lower boiling components such as gasoline. In general the temperature may be between about 850 and 975 f F., the heating time between about 250 and 1,000 seconds, and the pressure between about 50 and 600 p.s.i.g. Procedures of thisV type are described in standard textbooks and reference is made thereto for further details. See for instance Sachanen, Conversion of Petroleum, Second Edition, Reinhold Publishing Corporation, 1948, pages 252-254. Y

After visbreaking, the product is preferably subjected to distillation to remove lower boiling components such as gasoline formed during the visbreaking step. The

gasoline has an undesirable effect on the subsequent deasphalting step and it is advantageous, but not necessary, to remove it'vfor this reason. `Other components such as lfurnace oil may be removed if desired although we prefer `to retain such materials since they are improved by the subsequent hydrogenation.

The deasphalting step is carried out utilizing any known solvent deasphalting procedure. Such procedure is described in standard textbooks. See for instance Kalichevsky, Petroleum Refining with Chemicals, Elsevier Puby lishing Company, 1956, pages 388-396. Although We may use a conventional deasphalting solventsuch as propane, we prefer to employ an aliphatic hydrocarbon having 5 to 18 carbon atoms in the molecule. Thus we have found that hydrocarbons such as heptane or cetane may be added to the visbroken residual fraction and will cause precipitation ofthe asphaltic material. At the same time these solvents cause a larger amount of hydrocarbon substancesI to be retained in the oil portion of the feed. These additional hydrocarbons are of a resinous nature but we have found that during the subsequent hydrogenation they are converted into excellent catalytic cracking charge stocks. asphalting solvent the overall yields of high grade products are markedly'improved. The previous visbreaking step reduces the amount of deasphalting solvent required. One to four parts solvent to one of visbroken residual stock and preferably a one-to-one ratio is generally used. The deasphalting step may be carried out in the manner described in our application Serial No. 27,955, entitled Treatment of Petroleum Fractions, iled May 9, 1960,

v60' now Patent No. 3,053,750. This application discloses the deasphalting of residual stocks by heating a mixture of residual stock and deasphalting solvent to an elevated temperature and then adding an additional amount of deasphalting solvent to quench the mixture to a lower temperature. This causes improved precipitation and/ or settling of asphaltic materials. Howeverias indicated above, any conventional method of carrying out the deasphalting operation may be employed.

The visbroken-deasphalted residual stock is contacted with hydrogen in the presence of a hydrogenation catalyst such as a group VI left-hand column metal of the periodic system, their oxides and sulides. Similarly metals of the iron group, their-oxides and suldes-may Therefore by using this Aparticular type of de-V catalysts may be mixed with one another. For instance,

an advantageous mixture is a mixture of cobalt and molybdenum oxides. Another advantageous mixture is a mixture of nickel and tungsten oxides. These catalysts are deposited upon a porous catalyst carrier. Typical catalyst carriers are activated alumina, purnice, a silicaalumina cracking catalyst, etc. The pressure during the hydrogenation is maintained between about 500 and 3,500 p.s.i. and preferably is between about 1000 and 2000 p.s.i. The temperature may be between about 550 and 825 F. and preferably between about 650 and 800 F. A space velocity between about 0.3 and 10.0 volumes of charge stock per hour per volume of catalyst and preferably between about 0.5 and 4.0 is utilized. The hydrogen is present during the reaction in a ratio of between about 200 and 20,000 standard cubic feet and preferably between about 2000 and 10,000 standard cubic feet per barrel of visbroken-deasphalted residual charge stock.

` A preferred mode of hydrogenation as indicated above is to utilize a pressure of between about 1,000 and 2,000 p.s.i. This pressure is a relatively moderate pressure as compared with pressures heretofore used in destructive hydrogenation. Therefore the cost of the equipment is considerably lower than such destructive hydrogenation equipment. By operating in accordance with our invention, and utilizing a pressure of 2,000 to 3,500 p.s.i., it is possible to obtain thoroughgoing conversion into a catalytic cracking charge stock without using the relatively high pressures of the destructive hydrogenation prior art. Alternatively, if the cost of this higher pressure equipment is prohibitive, it is entirely feasible to obtain high yields of good quality furnace oil and catalytic cracking charge stock by carrying out the hydrogen treatment of our invention at a .pressure of between about 1,000 and 2,000 p.s.i. The cost of equipment when operating in this pressure range is much lower and at the same time markedly improved results are obtained as compared with previous operations carried out at similar pressures.

When operating in accordance with this iow pressure modification, i.e., 1,000 to 2,000 p.s.i. it is advantageous although not necessary to utilize a two-stage hydrogenation operation since it has been found that with such a two-stage hydrogenation process the yield of distillate products such as gasoline and furnace oil is substantially greater than with a single stage hydrogenation. The catalyst used in both of these two-stage hydrogenations may be the same. For instance, a cobalt-molybdate catalyst may be used in both stages. An advantageous combination of steps for this moderate pressure type of process is to use cobalt molybdate in the first stage in order to take advantage of the high desulfurization and hydrogenation activity of this catalyst and to use a nickeltungstate catalyst in the second stage in order to obtain a high degree of removal of nitrogen which, of course, has a harmful effect on the catalytic cracking catalyst if the product is subsequently catalytically cracked. The space velocity may be doubled as compared with a single stage process and still obtain greater yields. A space Velocity of 1.0 to 6.0 in each reactor is preferred when using this two-stage modification.

The product from the hydrogen treatment may be subjected to a distillation to separate desired components. The type of fractions separated will depend upon the end use. Ordinarily we prefer to subject the product to distillation to separate gasoline and furnace oil fractions and to obtain a residual fraction which may be catalytically cracked.

' FIGURE I of the accompanying drawings illustrates diagrammatic apparatus in which our invention may be carried out. Referring to the drawing, a residual feed to be treated in accordance with our invention is introduced through conduit 2 into visbreaking unit 3 where it is subjected to visbreaking in the manner herein described.

fil

- V'4 The visbroken feed is then introduced via conduit 5 into gasoline stripper 6 where gasoline formed during visbreaking is removed through conduit 7. Gasoline-free bottoms are withdrawn from stripper 6 through conduit 8 and introduced into deasphalting unit 9 where it is subjected to a deasphalting treatment as described above. Asphalt is removed from deasphalting unit 9 through conduit 10. The deasphalted feed is then introduced via conduit 11 into solvent distillation unit 12 where deasphalting solvent is removed through conduit 13 and recycled through conduit 15 together with make-up solvent introduced through conduit 17. The visbroken' and deasphalted feed is then introduced via conduit 14 into heater 16 in conjunction with a mixture of recycled and make-up hydrogen introduced through conduit 18. This mixture is heated to approximately reaction temperature in heater 16 and is then introduced via conduit 20 into hydrogenation reactor 22 which is filled with hydrogenation catalyst. In this first stage hydrogenation reactor, the hydrocarbon is subjected to hydrogenation under the conditions described, and the hydrogenated feed is then withdrawn through conduit 24, cooled in cooler 26 and then introduced into separator 23 via conduit 30. Hydrogen treated hydrocarbon is removed from separator 28 via conduit 32 and separated hydrogen is recycled by pump 34 through conduit 36. Make-up hydrogen is introduced through conduit 38 and a part of the hydrogen recycle is bled off through conduit 40 to maintain hydrogen purity.

The first stage product removed through conduit 32 from separator 28 is mixed with hydrogen introduced through conduit 44 and is introduced into heater 46. The heated mixture flows through conduit 48 into second stage hydrogenation reactor 50 which is also filled with a bed 'of hydrogenation catalyst. lHydrogen treatment takes place in this second stage-reactor in the manner described above, and the hydrogen treated product ows through conduit 52, cooler 54 and conduit 56 into separator 58. Hydrogen separated in separator l58 flows through conduit 60 into pump 62 and is recirculated via conduit 64. Make-up hydrogen is introduced through conduit 66, and a portion of the recycle hydrogen is bled oif through conduit 68 in order to maintain hydrogen purity.

The two-stage hydrogen treated product flows from separator 58 through conduit 70 and is introduced into fractionator 72 where it is subjected to fractionation to separate desired fractions. Thus gasoline is removed through conduit 74, light furnace oil through conduit 76,

l heavy furnace oil through Vconduit 78 and a bottom extraction through conduit 80.

The following example illustrates the benefits obtained by a mild visbreaking, i.e;, such as to form between about 4 and 20 percent gasoline, and especially between about 8 and 12 percent gasoline, as well as other advantages of our invention.

EXAMPLE Five samples of a residual fraction having the properties given in Table I were visbroken by heating to a ternperature between 875 and 980 F. and at a pressure of about 200 p.s.i.g. The time of heating was kept constant at about 370 seconds while temperature was varied in order to vary the thermal cracking and obtain gasoline formation varying from about 4 to 21 percent. The gasoline formed was removed. These gasoline-free products and a sample of theoriginal unvisbroken charge stock were then deasphalted utilizing heptane as a deasphalting solvent. The deasphalting was accomplished by adding various amounts of heptane to the visbroken Table l PROPERTIES OF RESIDUES AFTER VISBREAKING Vlsbreaking conditions:

Temperature, F 875 900 920 950 980 Residence time, seconds 370 370 370 370 370 Debutanized gasoline yield (percent by volume) 4.0 9.6 11.8 18.9 21.2 Properties of Gasolinefree Visbroken Residue:

API Gravity 6.8 7.0 V 6.3 5.9 4.1 3.8 Carbon Residue,

Conradson, percent. 19. 73 23.28 24.33 24.07 28.07 19.97 Viscosity Sco 8, 620 1, 440 1, 230 1, 060 1,310 1,350 Vanadium, p.p.m.. 136 155 162 168 185 190 Nickel, p.p.m 40.1 44.4 46.5 45.3 50.7 52.4

Table Il PROPERTIES OF RESIDUES AFTER DEASPHALTENING VITH T'WO VOLUMES 0F HEPTANE TO ONE VOLUME `OF GASOLINE-FREE VISBROKEN RESIDUE Asphaltene Yield:

Percent by weight 0 13. 8 19. 8 24.0 30. 6 34 5 Deasphaltened Residue Yield and Inspections:

Percent by weight. 100.0 86. 2 80. 2 764 0 69. 4 65. 5 API Gravity l 6.8 8. 6 9. 6 10. 7 10.4 13. 2 Carbon Residue, Conradson, percent 19.73 19. 15 16. 85 15. 61 15 57 12. 88 Viscosity, SUV at F., sec 8, 620 256 181 69.3 Vanadium, p.p.m 136 85.2 62. 4 50.0 26. 3 13. 4 Nickel, p.p.m 40.1 26.8 19.7 15. 5 10. 9 6. 3

l A visbroken product containing about percent gaso- 'line prepared and deasphalted as described above was ksubjected to distillation to remove the gasoline and portions thereof were contacted with hydrogen under the ,following respective conditions: at a pressure of 1000 Table III 1,000 2, 000 3, 000 p.s.i.g p.s.i.g p.s.i.g.

Gravity, API 26.1 25. 5 21.3 Viscosity SUV, sec

100 1 as 110 601 130 5o 71 255 Sulfur, percent 0. 33 0. 38 0.86 Nitrogen, percentm; 0. 14 0. 15 0.19 Carbon Residue, Conradson, percent 3. 37 2. 57 3. 74 Vanadium, p.p.n1 0.1 0.1 0. 1

It will be noted from Table II that visbreaking to between about 4 and 20 percent gasoline results in a marked improvement in asphalt removal in regard to the amount of solvent required. This effect reaches a maximum at about 10 percent gasoline as shown in the graphical presentation of these data in the drawing (FIGURE 2). It will also be noted that visbreaking toa gasoline yield of above about 20 percent does not improve the deasphalting operation in regard to the amount of solvent required. It will also be noted from the above data that the visbreaking operation, even when only a moderate amount of gasoline is formed such as 4 percent results in a marked improvement as compared with procedures in which no visbreaking is applied to the residual charge stock. The overall procedure of the invention is shown in Table III to yield a'product which can be used as a high quality catalytic cracking. stock low in metal impurities and nitrogen and having a reasonable carbon residue.

We claim:

The process which comprises subjecting a member of the group consisting of crudes, reduced crudes and topped crudes having an API gravity of below about 20 and containing a substantial amount of asphaltic materialsto visbreaking to form about l0 percent gasoline, removing the gasoline, deasphalting the remaining visbroken material with about 2 volumes of heptane to one volume of visbroken material, subjecting the `visbroken and deasphalted material to treatment with hydrogen in two separate stages in the presence of a member of the group consisting of suldes and oxides of group VI left-hand column and Vof iron group metals, sultides and oxides deposited upon a porous catalyst carrier, at a pressure between about 1000 and 2000 p.s.i., at a temperature between about 650 and 800 F., at a space velocity between about0.5 and 4.0, and at a hydrogen recycle rate of between about 2000 and 10,000 standard cubic feet per barrel of visbrokendeasphalted residual hydrocarbon charge stock, removing gasoline-furnace oil and catalytically cracking the remainder of the product.

References Cited in the iile of this patent UNITED STATES PATENTS 2,045,794 Pier ,Iune 30, 1936 2,459,465 Smith Jan. 18, 1949 2,559,285 Douce July 3, 1951 2,644,785 Harding et al. July 7, 1953 `2,697,681 Murray et al Dec. 21, 1954 2,727,853 Hennig Dec. 20, 1955 2,848,376 Oettinger Aug. 19, 1958 2,914,457 Beavon Nov. 24, 1959 2,926,129 Kimberlin et al Feb. 23, 1960 2,943,048 Rust et al. June 28, 1960 2,953,612 Haxton et al Sept. 20, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,132 ,088 May S, 1964 HaTold BeutheT` et al.

It is herebyl certified that error' appears in the above numbered pat- 4 ent requiring correction and that the sad'Letters Patent should read as corrected below.

Column 2, line 7, for "bisbreakng" read vsbreakng Column 5y Table lest Column, for "19.97" read 29.97

Signed and sealed this 13th day of October 1964.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

